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Abstract

Underwater exploration at Sistema Zacat? reached human limits when Jim Bowden descended to a depth of 289 meters April 6, 1994. In order to understand this karst system, unmanned robotic exploration is required to document the immense geometry of the underwater caves. The DEPTHX (DEep Phreatic THermal eXplorer) vehicle was developed with support from NASA to approach this problem, with the additional impetus to address robotic exploration in outer space. During the winter and spring of 2007, DEPTHX conducted three-dimensional (3D) underwater mapping missions of 4 cenotes in Sistema Zacat?: El Zacat?, Caracol, Poza Verde, and La Pilita. The detailed maps discovered no lateral tunnels connecting the cenotes, which are only 100-200 meters apart from each other. The deepest cenote, El Zacat? was bottomed out at a depth of 319 meters (339 m including above water cliff), making it the deepest underwater vertical shaft and second deepest underwater cave in the world. No side tunnels were discovered. However, the 3D data revealed geomorphic features of the cenotes to document how the karst system may have evolved through time. Spatial geochemical data collected contemporaneously during mapping missions indicate that water in the three warmest cenotes is extremely homogeneous, and the cooler cenote displays chemoclines similar to lacustrine type settings. The data collected by DEPTHX are being used with other types of geologic information to investigate the specific nature of hypogenic karstification that formed the cave system.